Treatment of oil wells



,Patented June 24, 1941 TREATMENT OF OIL WELLS 'Allen D. Gan-hon, Houston, Tex, assigninto The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application June 10, ms, Serial No. 212.976

at cum. (cl. ice-21) a 'lfhisinventlonrelates to the treatment of an oil well, and more particularly to the chemical treatment of the sand adjacent a producing well in order to render the sand preferentially wettable by oil to thereby increase the proportion of oil and decrease the proportion of water produced by that well.

It is recognized that ordinary sand is more easily wet by water than by oil. It is further recognized that oil producing sands are predominantly water-wet. When the pore spaces of an oil producing sand contain both water and oil'the fact that the sand surfaces are waterwet will cause the water to occupy the smaller capillaries and crevices to the exclusion of the oil, thereby limiting t e now of the oil to the larger capillaries only, this flow of oil through these capillaries being retarded because the pore spaces of the capillaries are substantially reduced in'cross section by the presence of the relatively immobile water film on the sand grains. The 011 now into and through the smaller capillaries and crevices is opposed by the lnterfacial tension between the oil and the water. My invention resides in a method of causing oil to flow through all of the capillaries and crevices of an oil producing sand by removing the water film from the walls of the capillaries and crevices and rendering the surfaces oil-wettable. In this manner'the flow of water into the well is retarded by the same force which obstructs the flow of oil through the average "water-wet oil producing sand.

In United States Patent No. 2,024,119, issued to William V. Viettl and Allen D. Garrison, there is disclosed and claimed a method of treating a producing sand of this character which is wet with water, by the depositing of a water and oil insoluble precipitate on the sand grains, which precipitate is of such character that it does not fill or block the pore space of the sand and is preferentially wettable by oil. v

The present invention constitutes an improvement over the method of said patent, and involves the pretreatment of the producing sand to dry or dehydrate the same so as to remove water from the pore space thereof and thus render thesand in more suitable condition to receive the preferentially oil wettable coating which is then deposited upon the sand grains. The present invention also involves the use of a different type of film coating from that disclosed in the patent. which coating has high effectiveness for the purpose intended and is particularly repellent to oil field brine.

In my copending application Serial No. 212,974 filed of even dat herewith, there is broadly disclosed and claimed the. dehydration of the produclng sand followed by the depositing of a water and oil insoluble coating which has preferential oil wettability upon the sand grains; and there is v specifically disclosed and claimed the method of dehydrating the sand by passing or blowing a heated gas therethrough, or by the combination of lowering a heated body into the well opposite.

the producing sand and then passing a gas into contact with the heated body and thence through the producing sand. In accordance with-the present invention and as claimed herein, the sand is dehydrated by chemical treatment. or by lowering a heated body into the well opposite the producing sand and preferably into a pool of oil collecting inthe bottom of the wellto highly heat this oil above the boiling point of water, and then forcing the highly heated oil through the sand. 7

Various methods of chemically dehydrating the sand in accordance with the present invention may be employed. There is preferably used a non-corrosive ydrating liquid which is oil soluble or miscibe when dry, but which has preferential solubility for water in the presence of the latter. For example, aliphatic ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone. and the like may be employed. Also organic anhydrides, such as the fatty acid anhydrides including acetic anhydride, propionic anhydride, butyric anhydride, and even mixed anhydrides such as acetyl formyl oxide and the like may be used. These are preferably employed in'the form of an oil solution, such as a crude oil or mineral oil distillate solution. Where an organic acid anhydride is used, the reaction may be facilitated by the addition of a small amount of a catalyst such as sulfuric acid, sodium acetate, zinc chloride and the like; which hastens the conversion of the anhydride in the presence of water to the corresponding acid.

A very satisfactory method of chemically dehydrating the sand involves a combination of the though a ketone of this character is miscible with oil when dry, in the presence of water in the sand space, a portion of the ketone will separate and show preferential solubility for the water and consequently enter and remove the water films about the sand grains, which films are in the main replaced by the oil of the solution. In order to remove the last traces of water, there is then introduced an oil solution of anacid anhydride. such as acetic anhydride, to which has preferably been added a small amount of a catalyst such as sulfuric acid. This is preferably followed by a final charge of oil to force out excess solution, and the excess solutions may be removed if necessary by pumping or bailing. The sand is now in condition to receive the preferentially oil wettable coating.

Alternatively, the sand may be dehydrated by lowering into the well by suitable cable an electrical heater or other highly heated body until this heater is positioned opposite the producing sand. By use of such a heater alone, a substantialdehydration of the sand for several feet or more be precipitated upon contact by and dilution with oil in the pore space of the sand. This method of introducing into the sand an oil miscible solution of a water and oil insoluble compound or'material, which material is precipitated upon contact by and dilution with oil in the pore space of the sand to form a strongly adherent film coating upon the sand grains which is preferentially wettable by oil, is broadly disclosed and claimed in my mentioned co-pending application Serial No. 212,974 filed of even date herewith. In the present application, there is claimed the particular water and oil insoluble bituminous or asphaltic material disclosed As a specific example of the present invention,

" the treatment 'ofa sixty-foot sand having a porosity, and which was water wet, to coat .the sandto a diameter of about two and oneabout the well bore may be accomplished. Or a heated body of this type may be lowered into oil accumulating in the bottom of the well .bore in order to heat this oil to a high temperature above the boiling point of water, preferably to the boiling point of the oil, and then this highly heated oil forced into the sand to secure further dehydration thereof. The water is thus converted into steam, which is driven outwardly to recondense in the colder parts of the sand away from the well bore. This alternative heating of the oil and then forcing the oil through the sand may be repeated several times to effect the dehydration desired. This latter method of de-- 1' hydration may be followed by a final chemical treat with a hehydrating agent, such as an oil solution of acetic anhydride as described above. although the heating and flushing with heated oil may be sumcient for most purposes.

In accordance with the present invention, there is deposited upon the sand grain s. film coating of a water and oil insoluble bitumen, such as may be obtained from as petroleum or coal tar pitch, asphalt, natural asphalt and the like. A very satisfactory material for this purpose is a modified asphalt produced by sulfurizing asphalt at higli temperatures, or by highly oxidizing asphalt by airblowing for extended periods of time and at temperatures to produce a resultant asphaltic material which is substantially insolu-' ble in crude oil'as well as in water. A satisfactory and cheap starting material for the production of this water and oil insoluble asphalt is a cracked petroleum residue, such as a cycle fuel oil or a heavy pitch derived from cracking operations.

In order to apply bituminous or asphaltic materials of this type in a convenient manner to the sand, an extract of the same in a suitable non-aqueous solvent is preferably utilized. For example, aromatic solventsof the character of benzol, toluol, xylene, light coal tar oil and the like may be employed. Likewise, chlorinated aromatic solvents such as chlorbenzene and nitrated aromatic solvents such as nitrobenzene may be used. Also, certain chlorinated aliphatic solvents such as carbon tetrachloride, or other solvents of high solvent power such as carbon disulfide may be used. Xylene, nitrobenzene, or a mixture of xylene and nitrobenzene is preferred for this purpose. It is found that these solvents will dissolve a substantial proportion of the modified asphaltic material which is insoluble in crude petroleum oil, and consequently will half to three feet. is described, Ten barrels of crude oil or a petroleum fraction having a higher viscosity than the oil present in the sand, were first introduced into the well and forced into the sand. Following this, there was introduced a charge of fifty barrels of oil containing 10% by volume of acetone dissolved therein. -This was followed by twenty barrels of .011 contain,"

ing 10% by volume of acetic anhydride and three gallons of concentrated sulfuric acid The well was then flushed with twentybarrels of oil; and this was followed byintroducting two barrels of a 10% carbon tetrachloridesolution of an oil insoluble sulfurized asphalt of the charaster-described above. The treatment was completed by finally introducing 100 barrels of oil to flush out the solutions and render the sand immediately about the-well bore wet with 011.

As illustrative of the efiiciency of the. coating of the present invention in repelling the passage of water or brine facilitating the flow of oil, the following experiment was performed. A producingsand was coated with an oil insoluble asphalt of the characterdescribed above. This sand was packed into a Buchner funnel mounted at an angle tothe vertical, so that the upper exposed surface of the sand in the funnel was on an incline. There was then poured into the funnel an oil field brine so as to form a layer covering only about half of the exposed surface of the sand. This brine remained in place on the sand without passing through the filter. There was then poured into the funnel some'crude/oil so as to form an upper layer over the brine and to cover the remaining exposed surface of the sand, thereby giving substantially equal access of the brine and the crude oil to-the sand. It was found that the crude oil ran readily through the filter with substantially no occluded water or brine, and that the brine remained in place on the filter after the oil had passed therethrough.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of treating anoil well to convert a water-wet producing sand to one which is preferentially wettable by oil, which comprises drying a substantial volume of the said producing sand surrounding the bore hole of the well to remove water from the pore space thereof, and then coating the sand grains of -said producing sand without blocking that sand with a film coating of a water and crude oil-insoluble bitu- 'men which is preferentially wettable by oil, to

thereby increase the proportion of oil relative to water produced from said sand.

2. The method of treating an oil well to convert a water-wet producing sand to one which is preferentially wettable by oil, which comprises depositing on the sand grains of said sand without blocking the same a film coating of a water and crude oil-insoluble bitumen which is preferentially wettable by oil, to thereby increase the proportion of oilrelative to water produced from said sand. v

3. The method as defined in claim 2, in which the water and crude oil-insoluble bitumen is a modified asphalt selected from the group consisting of sulfurized asphalt and highly oxidized asphalt.

4. In the treating of an oil well to convert a water-wet producing sand to one which is preferentially wettable by oil, the method which comprises introducing into the well and into the said producing sand throughout a substantial volume of said producing sand surrounding the bore hole of the well an organic solvent extract of a water and crude oil-insoluble bitumen, to thereby deposit on the sand grains of said produclng'sand without blocking that sand a film coating of the said bitumen, with resultant increase in the proportion of oil relative to water produced from said sand.

- 5. The method as defined in claim 4, in which the organic solvent extract contains a solvent selected from'the group consisting of aromatic,

chlorinated aromatic, nitrated aromatic anti volume of the said producing sand surroundin the bore hole of the well with a water and crude oil-insoluble film coating which has preferential oil wettability, in combination with the step of chemically dehydrating the said producing sand by passing therethrough a mineral oil solution of an organic liquid which is miscible with mineral oil when dry but which has preferential solubility for water in the presence of the latter.

9. The method'as defined in claim 8, in which the said producing sand is chemically dehydrated by passing therethrough a mineral oil solution of an organic compound selected from the group consisting of aliphatic ketones and organic acid anhydrides.

10. The method as defined in claim 8, in which the said producing sand is chemically dehydrated by passing therethrough a mineral oil solution of acetone.

11. The method as defined in claim 8, in which the said producing sand is chemically dehydrated by passing therethrough a mineral oil solution of an organic acid anhydride containing a catalyst promoting the conversion of the anhydride to the corresponding fatty acid inthe presence of water.

12. The method as defined in claim 8, in which the said producing sand is chemically dehydrated by passing therethrough a mineral oil solution of acetic anhydride containing a small amount of sulfuric acid.

13. The method as defined in claim 8, in which the said producing sand is chemically dehydrated by passing therethrough a mineral oil solution of an aliphatic ketone followed by a mineral oil solution of a fatty acid anhydride.

14. The method as defined in claim 8, in which the said producing sand is chemically dehydrated by flushing the said sand with mineral oil, then passing through the said sand a mineral oil solution of acetone, and finally passing through the said sanda mineral oil solution of acetic anhydride.

15. In the treating of a well to remove water therefrom and to dehydrate a formation surrounding the bore hole of the well, the method which comprises introducing into the well and into contact with the formation a mineral oil solution of an organic compound which is miscible with mineral oil when dry but which has preferential solubility for water in the presence of the latter.

16. The method as defined in claim 15, in which the mineral oil solution contains an organic liquid selected from the group consisting of allphatic ketones and organic acid anhydrides.

17. Themethod as defined in claim 15, in which the mineral oil solution contains acetone. 7

18. The method as defined in claim 15, in which the mineral oil solutioncontains a fatty acid' anhydride and a catalyst promoting the conversion of the anhydride to the corresponding fatty acid in the presence of water,

.19. In the treating of a well to remove water therefrom and to dehydrate a formation surrounding the borehole of the well, the method which comprises introducing into the well and into contact with the said formation a mineral oil solution of an aliphatic ketone followed by a mineral oil solution of an organic acid anhydride.

20. In the treating of a well to remove water therefrom and to dehydrate a formation surrounding the bore hole of the well, the method which comprises introducing into the well and into contact with the said formation a flushing oil, then introducing a mineral oil solution of acetone, andfinally introducing a mineral oil solution of acetic anhydride.

ALIEN n. GARRISON.

DISCLAIMER [OfiicioZLGczette October 19, 1943.]

Disclaimer Tex. TREATMENT or OIL WELLS. Patent filed September 22, 1943, by the assignee,

DISCLAIMER 2,246,725.Allen.D. Garrison, Houston, Tex. TREATMENT or On. WELLs. Patent dated June 24, 1941. Disclaimer filed September 22, 1943, by the assignee, The Texas Company.

Hereby disclaims claims 8, 9, and 10 pfsaid patent.

[OfiiciallGazette October 19, 1943.] 

